Sliding contact device for tuning coils



July 7, 1959 R. T. ADAMS ET AL 2,394,233

suomc CONTACT DEVICE FOR TUNING cons Filed Dec. 20, 1954 INVENTORS ROBERT 7. ADAMS JACK 6. HARVEY BY 540 N Y United States Patent SLIDING CONTACT DEVICE FOR TUNING COILS Robert T. Adams, Short Hills, N.J., and Jack B. Harvey, New York, N.Y., assignors to International Telephone and Telegraph Corporation, Nutley, NJ., a corporation of Maryland Application December 20, 1954, Serial No. 476,416

3 Claims. (Cl. 336-149) This invention relates to tuning coils and more particularly to a sliding contact device for such coils.

An object of this invention is to provide an improved sliding contact device for tuning coils which lends itself to easy fabrication and provides substantially constant contact pressure as said device is moved over variations in the surface of the coil.

Another object of this invention is to provide a sliding contact device having a plurality of contact elements for engagement with the turns of a coil, the engagement pressure of which may be easily adjusted, by adjusting the circumferential tension of said device, and a resilient characteristic to enable the contact elements to follow variations in the surface of the coil and yet maintain the desired engagement between the contact elements and the turns of the coil. The resilient characteristic of said contact device, radially and circumferentially, insures essentially constant contact pressure through its entire circumference regardless of the degree of movement or floating exhibited by said contact device even when the relative axes of the coil, driving mechanism, and contact device are misaligned.

A feature of this invention is the provision of a band of conductive material adapted to encircle a tuning coil to function as a sliding short therefor, said band being corrugated and having a plurality of contact elements disposed in spaced relation circumferentially thereof for engagement with the turns of said coil. The corrugated shape of the band gives it a resilient characteristic to insure continuous contact pressure between the contact elements and the turns of the tuning coil by permitting radial and circumferential freedom during axial movement of said band regardless of variations in the surface of said coil and misalignment of the axes of said band and the tuning coil.

Other features of this invention include the cross-sectional shape of the corrugated bands which may take a sinusoidal, a square, a triangular or a re-entrant configuration, the positioning of a contact element in the form of a protuberance on certain ones of the ridges thereof adjacent one edge of the band, and a means for moving the contact device axially of the coil which constrains the contact device only for axial movement thereof and yet enables radial and circumferential res'ilience'to insure continuous contact pressure between the contact elements and the turns of the coil regardless of variations in the surface of said coil and misalignment of axes of the coil, the contact device and the means for moving the contact device.

The above-mentioned and other features and objects of this invention will become more apparent by reference to the following description taken in conjunction with the accompanying drawings, in which:

Fig. 1 is a plan view of a strip of material utilized in the contact device of this invention prior to being adapted to encircle a tuning coil;

Fig. 2 is an end view of an embodiment of the sliding contact device of this invention;

Patented July 7, 1959 Fig. 3 is a longitudinal cross-sectional view taken along line 33 of Fig. 2; and

Figs. 4, 5 and 6 are end views of still other corrugations which may be imparted to the material utilized in the contacting device of this invention.

Referring to Figs. 1, 2 and 3, a band of conductive material 1 is shown which is formed to provide the contact device of this invention. Band 1 is shaped to have a corrugated configuration, the corrugating process producing ridges 2 and furrows 3. The band 1 is further processed to provide on ridges 2 contact elements 4. Contact elements 4 are pictured as being on each of the ridges adjacent one edge of strip 1. However, the contact elements 4 may be disposed on only certain ones of the ridges 2 and need not be disposed adjacent an edge of band 1 but may be disposed at any point along the ridges between the edges of the band. It is preferred, however, that the contact elements appear on each ridge 2 and be disposed adjacent an edge of band 1 to form a straight contact line or leading edge which is parallel to the edge of band 1. The straight contact line provided by elements 4 assures a contact device for a tuning coil which enables a relatively fine adjustment of that portion of the tuning coil which is being shorted or grounded out by the contact device.

The band 1, including the corrugation thereof and the forming of the contact elements 4, may be pro duced in a manner to provide a continuous band of conductive material which may be stored upon a reel or other such storage device. The contact elements 4 may be formed on ridges 2 by a machining process to dimple or otherwise deform the ridges 2 to provide a protuberance thereon. The contact elements 4 may also be formed, if desired, by building up the ridges 2 at the desired location.

The conductive band i, which in a successful reduction to practice was composed of coin silver, an alloy of 96% ilver and 10% copper, is cut in the desired length to encircle a tuning coil 6 as depicted in Figs. 2 and 3. The desired length of band 1 is adapted to form contacting device 5 by overlapping a portion of band 1 and spot welding these overlapped portions as indicated at 7. In practice, contact 5 is formed from band 1 as indicated above, but prior to engagement with the turns of tuning coil 6, the contacting device is sized by means of a mandrel of appropriate diameter. This sizing operation adjusts the diameter of device 5 for engagement with the turns of coil 6 and likewise the contact pressure which wili be exerted between elements 4 and the turns of coil 6 due to the circumferential tension of the band 1. At the time that the contacting device 5 is sized on a mandrel, a support 8 for moving the band 1 axially of a coil is secured to the edge of the contact device 5 opposite the contact elements 4. After contact device 5 has been sized and is provided with a means for movement axially of the tuning coil, the assembly will be positioned to encircle tuning coil 6. The contact elements 4 will engage the turns of coil 6 such that more than one contact element is in engagement with one of the turns of the coil 6, some of which will in effect bridge two of the turns.

It will be recognized that the turns of coil 6 present variations in the surface of the coil and that a rigid contact device could not follow these surface variations and maintain consistent contact with the turns as the device is moved axially of the coil. However, the employment of a band of conductive material having a corrugated shape imparts to contact device 5 a radial and circumferential resilient characteristic which will follow the variations in the surface of the coil 6 and will accommodate misalignment of the axes of coil 6, contact device 5 and support 8. This resilience insures continuous contact and substantially constant contact pressure between elements 4 and the turns of coil 6 during axial movement of device 5.

As shown in Figs. 2 and 3, the movable support 8 is provided 'with rods 9 capable of radial and tangential flexibility, spot welded or otherwise secured to the furrows of contact device adjacent the edge thereof opposite the contact elements 4. These fingers 9 are Welded or otherwise secured to a ring 10 carried by an annular member 11 having apertures 12 and 13 which are threaded to accept worm gears 14 and 15, respectively. Worm gears 14 and 15 are driven by a motor drive 16, in a manner to move the member 11 and, hence, contact device 5, axially of coil 6 for adjustment of the number of turns which are shorted or grounded out.

'The means to move contact device 5 is not restricted to the means disclosed in Figs. 2 and 3. Another arrangement which could be utilized to drive contact device 5 axially of coil 6 comprises a cylindrical member, the Wall of which is U-shaped in longitudinal crosssection, the legs of the U-shaped portion being disposed in a manner to engage the trailing and leading edges of contact device 5 to constrain contact device 5 for only axial movement thereof, as the cylindrical member is driven by a worm gear arrangement or a rack and pinion arrangement. In the employment of such a cylindrical U-shaped member for movement of contact device 5, the constraining force thereof for axial movement must not be such as to prevent radial and circumferential movement of the flexible contact device 5, otherwise, the desired resilient characteristic thereof will be impaired and the contact elements will not be allowed to follow the variations in the surface of the coil 6 or compensate for misalignment of the axes of the various elements of the combination. It should be pointed out that any means may be utilized to move the contact device 5 axially of coil 6 provided that the flexibility of contact device 5 is constrained only for axial movement thereof and that radial and circumferential movement or flexibility of the contact device is not impaired by the means for axial movement.

The end view of Fig. 2 illustrates that the corrugation of band 1 is substantially sinusoidal in configuration. This is not necessarily the only configuration of the corrugation of band 1. Figs. 4, 5 and 6 show other conductive bands having diiferent shapes of corrugation. Fig. 4 illustrates a corrugated band lla having a substantially square configuration with contact elements 4a being disposed on the ridges 2a in substantially the same manner as described in connection with Fig. 1. Fig. 5 illustrates a band of conductive material 11b having a triangular corrugated configuration with the contact elements 4b being disposed on ridges 2b substantially as described in connection with Fig. 1. Fig. 6 illustrates a band of conductive material llc having a reentrant type of corrugation with the contact element 4c being disposed on ridges 2c substantially as described in connection with Fig. 1. This latter configuration will provide a substantially continuous contact and yet has the desired flexibility necessary to follow variations in the coil surface.

While we have described above the principles of our 4 invention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of our invention as set forth in the objects thereof and in the accompanying claims.

We claim:

1. A tuning arrangement comprising an inductive tuning coil and a sliding contact device including a band of conductive material surrounding said coil, said band having alternately spaced ridges and furrows running axially of the coil, and a plurality of contact elements disposed on certain of said ridges facing said coil in a plane perpendicular to the axis of said coil, and means for mounting said band for axial movement along said coil, the alternately spaced ridges and furrows giving said band a radial and circumferential resilient characteristic to insure constant contact pressure between said contact elements and the turns of said coil as said ,contact elements slide across one turn into engagement with the adjacent turn.

2. A tuning arrangement comprising an inductive tuning coil and a sliding contact device including a band of conductive material surrounding said coil, said band hav ing alternately spaced ridges and furrows running axially of the coil, said ridiges being provided with protuberances facing said coil in a plane perpendicular to the axis .of said coil, and means for mounting said band for axial movement .along said coil, the alternately spaced ridges and furrows giving said band .a radial and circumferential resilient characteristic to insure constant contact pressure between said protuberances and the turns of said coil as said protuberances slide across one turn into engagement with the adjacent turn.

3. A tuning-arrangement comprising an inductive tuning coil and a sliding contact device including a :band of conductive material surrounding said coil, said band being corrugated to provide therein ridges and furrows, and a plurality of contact elements disposed in spaced relation circumferentially about said band facing said coil. in a plane perpendicular to the axis of said coil, and means for mounting said band for axial movement along said coil, said contact elements including protuberances formed in certain of said ridges, the corrugated shape of said band giving said band a radial and circumferential resilient characteristic to insure constant contact pressure between said contact elements and the turns vof said coil as said contact elements slideacross one turn into engagement with the adjacent tutrn.

References Cited in the file of this patent UNITED STATES PATENTS 1,936,469 Hill Nov. 21, 1933 2,007,489 Westberg July 9, 1935 2,363,132 Lightfoot et al Nov. 21, 1944 2,444,433 Erb July 6, 1948 2,451,809 Clark Oct. 19, 1948 2,490,253 Buchanan Dec. 6, 1949 2,706,230 Bourns et al Apr. 12, 1955 FOREIGN PATENTS 711,175 Great Britain June 23, 1954 835,465 Germany Mar. 31, 1952 

